The present invention relates to clutches and transmissions for transmitting torque, and to clutches adapted to be used in a transmission system such as a transmission system including a continuously variable transmission.
A U.S. Pat. No. 5,593,016 (corresponding to a published Japanese Patent Application Publication (Kokai) No. H07-279992) shows a wet type multiple disc clutch including therein a torque cam mechanism interposed between a clutch disc pack and a clutch piston, and constructed to serve as a one-way clutch.
However, once this clutch is engaged, the clutch remains engaged until a driving force is applied in an opposite direction, even if the clutch piston is withdrawn by drainage of fluid pressure. In this clutch, relative rotation on both sides of the cam mechanism, required for the effect of a cam mechanism, is produced by pressing the torque cam mechanism against the clutch disc pack by applying the fluid pressure on the piston. Accordingly, even after the fluid pressure is removed, the torque cam mechanism continues pressing the clutch disc pack until a driving force in the opposite direction is applied.
It is an object of the present invention to provide a clutch apparatus capable being restored to a disengaged state by switching a clutch actuator, such as a hydraulic actuator including a clutch piston, from an actuated state to an unactuated state.
According to the present invention, an apparatus (such as a clutch apparatus or an infinitely variable transmission) for transmitting torque, comprises: a clutch pack of friction elements; a clutch actuator to produce a clutch action to compress the clutch pack axially for clutch engagement, the actuator comprising a clutch piston to move toward the clutch pack when the clutch piston is actuated; and a torque cam mechanism interposed between the clutch pack and the clutch piston. The torque cam mechanism comprises a cam member to extend the torque cam mechanism axially in response to a relative rotation between both ends of the torque cam mechanism. The torque cam mechanism is arranged to compress the clutch pack axially when the clutch piston is actuated and simultaneously the torque cam mechanism is extended axially.
According to another aspect of the present invention, a clutch apparatus comprises: first means for making driving connection for clutch engagement by surface friction when compressed and breaking the driving connection when released; second means for compressing the first means to effect the clutch engagement; third means for producing a clutch action to force the second means to compress the first means when the third means is actuated; fourth means, interposed between the first means and the third means, for allowing the third means to force the second means to compress the first means through the fourth means by producing an axial force to force the second means away from third means toward the first means when the fourth means receives drag torque from the first means through the second means; and fifth means for preventing the first means from being compressed even if the axial force is produced by the fourth means in response to the drag torque when the third means is not actuated.
According to still another aspect of the present invention, a clutch apparatus comprises: a clutch pack of clutch discs; a pressure member to compress the clutch pack axially for clutch engagement; a first piston to produce a clutch action to compress the clutch pack with the pressure member when the first piston is actuated by a first fluid pressure; a second piston arranged to be moved from a first position to a second position toward the clutch pack by the first piston when actuated, and further from the second position to a third position toward the clutch pack when the second piston is actuated; a friction reducing device, interposed between the second piston and the pressure member, to increase an axial distance between the pressure member and the second piston with the aid of a contoured cam surface when the second piston and the pressure member are rotated relative to each other, and thereby to push the pressure member to compress the clutch pack when the second piston is held at the second position; a shift stopper to prevent the clutch pack from being compressed when the distance between the pressure member and the second piston is not increased, by holding the second piston at the second position by limiting axial movement of the first piston; a return spring to normally hold the second piston at the first position to prevent the clutch pack from being compressed irrespective of whether the distance between the pressure member and the second piston is extended or not.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.